In-Laws and Shabbat Law

What is the halachic source of matrilineal descent?
Why are we set against patrilineal descent when all of our ancestors
in the Torah are referred to as so and so son of so and so, referring
only to the father's name?

Dear Nathan Silberstein,

In the time of the Patriarchs it appears that descent
followed the father. However, the period of the Patriarchs was
before the giving of the Torah on Mount Sinai. It was only with
the revelation on Sinai that the Jewish people received their
legal system. Therefore it is impossible to bring Halachic, legal
proofs from the Patriarchs. Our source for Halacha is the Written
and Oral Torah.

The Mishna in Tractate Kiddushin 66b states that
if a child's mother is not Jewish, then the child is not Jewish.

The Babylonian Talmud, Kiddushin 68b, derives this
Halacha from a verse in Deuteronomy 7:1-5, which also contains
the prohibition against intermarriage. "When the L-rd your
G-d brings you to the land that you will inherit, many nations
will fall away before you; the Hittites, the Girgashites, the
Amorites, the Canaanites, the Prizites, the Hivites and the Jebusites...
And you shall not marry with them; do not give your daughters
to his sons and do not take his daughters for your sons. For
he will turn your son away from me and they will worship other
gods...." The Talmud points out that the verse only seems
to be concerned with the son of the Israelite woman being
turned away, "for he (the gentile)" will turn your son
away. It does not seem to be concerned that "she (the gentile)
will turn your son away." The implication is that the son
of the Jewish woman and gentile man is still considered "your
(the Jewish grandfather in this case) son," but in the case
of a gentile woman married to a Jewish man, the child is not considered
"your son" and therefore there is no concern about his
turning away. This follows Rashi and Tosfot Ri Hazaken in their
explanation of the Gemara.

Tosfot (ad loc. "Amar
krah") offers a number of different methods of derivation
from the verse, but agrees with the conclusion. This law is also
found in the Mishna in Yevamot (ch. 2, 21a): "He counts as
a brother in every respect unless he was the son of a maidservant
or of a gentile woman."

This halacha is codified in the Code of Jewish Law,
Even HaEzer 8:5, and in Maimonides' Mishneh Torah, Laws of Forbidden
Relationships, 15:4. Maimonides states: "This is the general
rule: The status of an offspring from a gentile man or from a
gentile woman is the same as his mother's; we disregard the father."

Another source in the Torah is the verse in Leviticus
24:10: "the son of an Israelite woman went out - and he
was the son of an Egyptian man." This person is described
as being "in the midst of the community of Israel" -
in other words, Jewish.

Probably the most explicit verse against patrilineal
descent is in the book of Ezra 10:2-3: Some of the Jews who had
returned from the exile declare, "We have trespassed against
our G-d and have taken foreign wives of the people of the land.
Yet, there is hope in Israel concerning this thing. Therefore,
let us make a covenant with our G-d to put away all the wives
and such as are born to them, according to the counsel
of the L-rd and of those who assemble at the commandment of G-d;
let it be done according to the law."

Sources are also in Midrash Rabbah, Numbers, 19,
and Jerusalem Talmud, Kiddushin 3:12.

Do we ignore the father completely? Certainly not.
The father is the one who determines what tribe the child is
from. That is: Kohen, Levi, Yisrael. Also, in determining royalty
and other leadership roles among the Jewish people we go from
father to son.